The invention relates to a gripping device for a manipulation system comprising a robot for receiving parts and feeding a manufacturing plant with a workpiece from a readied stack of workpieces. The invention also relates to a method for operating the gripping device.
In the manipulation of workpieces with automated manipulation systems, so-called robots, where the workpieces are seized and lifted by means of a gripping device from a made-ready position and then have to be fed to a manufacturing system where they are worked, problems often occur with the feed from a stack of cut or punched flat workpieces such as metal sheets, for example due to surface contamination caused by a film of cutting or punching oil, causing the sheets to adhere to each other, so that two or more sheets are picked up from the stack by the gripping device, for example a suction or magnetic gripper, instead of only one single sheet, leading to interference with the production process.
Possibilities for remedying such a situation are known in the prior art, one such possibility being to equip the gripping device with a weight sensor in order to determine the weight of the seized sheets lifted on the gripping device with the help of the parameters stored in a computer, and to then separate the workpieces, if necessary.
Another possibility offered by the prior art is to carry out an optical measurements, for example of the thickness after the sheet has been seized, and to then determine the number of workpieces seized based on the weight with the help of the parameters stored in a computer, in order to subsequently separate the workpieces, if need be.
Furthermore, ultrasound, eddy current and magnetic measuring methods are known, by which the total weight is determined, and the further course of action is then determined as in connection with an optical measurement.
Moreover, it is known also to divide the workpieces into single pieces before they are seized if such pieces stick together. However, the devices required for such separation require high expenditure in terms of mechanical components, and their operation is connected with increased controlling expenditure.